1. Field of the Invention
The present invention relates to an image forming apparatus comprising a cleaning mechanism designed to clean up residual toner remaining on an image bearing surface.
2. Description of the Related Art
Heretofore, there has been known an image forming apparatus provided with a cleaning mechanism designed to remove and clean up residual toner remaining on a transfer belt serving as an image bearing member, as disclosed in JP 2000-131969A. This cleaning mechanism comprises a main cleaning device adapted to generally clean an image bearing region of the transfer belt which is being circulatingly moved, and an auxiliary cleaning device disposed in a vicinity of and on an upstream side relative to the main cleaning device.
The auxiliary cleaning device is adapted to locally clean the image bearing region in a specific zone corresponding to a mark image which is created on a widthwise part of the image bearing region to determine image forming conditions on the transfer belt. This cleaning mechanism allows even a specific zone having a locally increased cleaning load to be effectively subjected to a cleaning process, and therefore has a potential to achieve a more adequate cleaning process for the transfer belt.
However, the auxiliary cleaning device of the above cleaning mechanism is designed to simply perform a preliminary cleaning process only for the specific zone corresponding to the mark image in the transfer belt. This is not enough to reliably remove residual toner on the transfer belt. Moreover, the auxiliary cleaning device is fixed in an immovable manner relative to the transfer belt. Consequently, a contact pressure of the auxiliary cleaning device against the transfer belt will fluctuate depending on vibration of the transfer belt which is being circulatingly moved. The fluctuation in the contact pressure of the auxiliary cleaning device leads to a variation in cleaning performance of the auxiliary cleaning device, and thereby causes difficulty in uniformly removing residual toner on the transfer belt on a constant basis.